Catalytic photopolymerization process and compositions



, polymerization.

Patented Apr. 25, 1950 UNITED STATES PATENT OFFICE CATALYTIC PHOTOPOLYMERIZATION PROCESS AND COMPOSITIONS Carrol C. Sachs, North Holl West Los Angeles, Calif., H. Kerr & 00., Los An tion of Nevada ywood, and John Bond,

assignors to Alexander geles, Calif., a corpora- 20 Claims. (Cl.204-162) The photochemical polymerization of ethylenically unsaturated monomers and low molecular weight polymers oi'such unsaturated monomers has been described, in the prior art and it has also been shown that certain compounds have they property or catalyzing their photochemical Photopolymerization catalysts have been suggested in the prior art, which contain chromophor groups or groups which form chromophor groups in the course of the polymerization. The latter type is hereafter called chromophor formers. It is obvious that when used with clear, 1. e., uncolored, translucent or transparent resins, the polymerization by the aid of such catalysts imparts some color to the polymerized resins.

We have discovered that the haloalkyl substituted polynuclear aryl hydrocarbons of condensed benzene ring type are active photopolymerization catalysts when employed to initiate or accelerate the photochemical polymerization of photopolymerizable organic compounds containing resinophoric groups. Certain of these catalysts are colorless and do not impart color to the polymer during the polymerization process in which the monomer or partial polymer is polymerized to a polymer of higher molecular weight.

It is generally well known that certain of the organic resinophoric compounds are light-sensitive in that light reduces the induction periods or increases the rate'of polymerization. Such compounds are those resinophoric compounds which contain radicals which include an ethylene linkage and which polymerize according to the vinyl type of polymerization. Such compounds have been classed as vinyl types (see Plastics, Resins and Rubber, by Paul 0. Powers, Chemical and Engineering News, Oct. 25, 1946, vol. 24, No. 200, Page 2784).

These include the acrylic resins, i. e., resins produced by polymerization of acrylic acid or derivatives of acrylic acid, for example, methyl acrylic acid, or methyl, ethyl, butyl acrylate, methyl methacrylate, ethyl methacrylate, butyl .methacrylate, isobutyl methacrylate. Such types also include styrene and its derivatives, for example, styrene and the alkyl nuclear substituted styrenes, such as ortho or metamethyl styrene or the chlorinated styrenes. It also includes chloroprene. This typealso includes the allyl compounds, such as allyl alcohol and allyl alcohol condensed with polybasic acids, as in allylmaleate or allyl phthalate or the condensate of allyl alcohol with polybasic acids and polyhydric alcohols to form suitable copolymers.

Such types also include vinyl acetate, vinyl halides, for example, vinyl chloride and vinylidene halides, for example, vinylldene chloride.

The addition of a small amount of the photopolymerization catalyst of our invention to the photopolymerizable monomers or partial polymers positively catalyzes the photopolymerization materially.

These catalysts are also active for mixed monomers or mixed partial polymers or for the polymerization of mixed monomers or mixed partial polymers capable of copolymerization. Our catalysts catalyze the photopolymerization of copolymers of esters of unsaturated glycols such as ethene or butene diols and unsaturated dicarboxylic acids, such as maleic, fumaric or itaconic acid, or copolymers thereof with the above vinyl type of resinophoric compounds, as, for example, vinyl acetate or styrene.

Thus, these catalysts are active in the photopolymerization of the allyl esters and particularly the allyl esters of the polycarboxylic acid, such as diallyl maleate 0r diallyl phthalate and their copolymers with the above vinyl type resinophors.

Polyglycol esters of acrylic and methacrylic esters and their copolymers with the resinophors of the vinyl type as stated above are also included.

Cross linking agents may be employed which contain two or more terminal ethylene linkages CH2=C which may enter into a vinyl type of polymerization. These include ethylene dimethacrylate; allyl methacrylate; methallyl methacrylate; ethylene glycol dimethacrylate; hexamethylene glycol dimethacrylate; dimethallyl carbonate; and similar compounds.

All of the above resinophoric compounds contain C=C (ethylenic) linkages in resinophoric arrangement. As stated above, certain of them are of the vinyl type and others, particularly certain of the ester types, are not all strictly classifiable as vinyl type polymers, in that their polymerization is not strictly of the vinyl type, since cross linkage to form three-dimensional resins is also possible. These may be classed as the non-vinyl ester type resinophors. They are all classifiable as ethylenically unsaturated resinophors and since, especially when catalyzed by our catalysts, they are photochemically polymerizable, they may thus be classed as ethylenically unsaturated photochemically polymerizable resinophoric compounds.

The photochemical polymerization catalysts of our invention are derivatives of the polynuclear hydrocarbons with condensed benzene ring including the derivatives of naphthalene, anthracene, phenanthrene, pyrene, chrysene, and other condensed polynuclear aromatic hydrocarbons.

The derivatives of these polynuclear hydrocarbone which form the subject of this invention are the haloaikyl substituted polynuclear hydrocarbons with condensed benzene rings where the halogenisinthelpositioninthesidechaimie. attached to the carbon which is attached to the ring. These include the haloalkyl, for example, the chlormethyl or bromo-methyl or chloro-ethyl or bromo-ethyl or higher haloalkyl side chains in the alpha or beta position in naphthalene, anthracenc, phenanthrene. or the gamma (0 or 10) position of anthracene or phenanthrene.

Such compounds may also contain other substituents such as the non-polar alkyl substituthe photopolymerization of the ethylenically unsaturated photochemically polymerisahle raino phorlc compounds, including photopolymerisation of such resinophors with others of the vinyl type or or the non-vinyl ester type. For of further description and definition, we shall refer to such catalytic compounds as haloalkyl poiynuclear aromatic compounds containing condensed benzene rings to include such compounds as well as the specii'ied substitution products.

We prefer, when we desire to produce acolorless p lymer, such as a clear tramparent material, or, where the color imparted by the catalyst would be undesirable to employ such compormds which do not contain th active chromophor groups which impart strong color to the pofylner or do not contain groups which, on reaction, form the strong chromophor groups. Such strong chromophor groups include the following:

(-N=N) aso (0:8) thio; (N=0) nltroao N-N-O story 0. N mm -OH-N- asomethane 0 The polynuclear hydrocarbons, having condensed rings greater than 2, are more sensitive to chromophor action than is naphthalene, in that weak chromophor groups, which do not impart color to naphthalene, may impart color to anthracene, phenanthrene, etc.

Certain groups such as the C=O carbonyl are known to be chromophoric, when present in multiple or when present together with the so-called auxochrome groups. These aunochromegroups may not of themselves impart color but when present, in addition to the chro.-'

mophor, augment the action of the chromophor group.

These auxochrome groups include the amino or substituted amino groups, the hydroxyl and the methoxy groups, or the halogen group. We, therefore, employ. when we wish to avoid imparting color to the resin, a haioalkyl substituted polynuclear aromatic containing condensed ben- 4 groupsor,ifsosubstituted,notsubstitutedhy chromophor or chromophor-forming group or ups.

Afurtherdeairablepropertyisthatthecaw lystbesoiuhleoroolloidally dispersibleinthe monomerorpartialpolymerinwhichitistobe mm Ixamples of the photochemical catalytic compotmds of our invention are alpha-chiormetlwl tionandtheotherinthehetapositionand thecaseoftheanthraoeneorphenanthrene fthechlormethylsmaybeinthealphaor betapositionandtheotherinthegamma position. Bromomethyioriodo-methylanalogms ofeachoftheabovechlormethylcompoundsare also above, we may employ haloalkyia of longer carchain length, such as haloethyl, halopropyl halobutyl compounds and higher haloalkyls ofhigherchalnlengthsolongasthechainin lengthorhranchingissuchasnottoimpairthe dispersibility or solubility of the catalyst in the monomer or partial polymer. We prefer to employ as haloalkyl substituent those of short alkyl chainlengths,forexample,thoseoi'lessthan5 carbon atoms in uninterrupted carbon-carbon The haloalkyl polynuclear aromatic compounds containing condensed benzene rings, wherein halogenischosenintheseriesoftheperiodicarrangement of elements oi series number higher than 1. i. e., iodine, bromine or chlorine, are included as preferred as the halogen substituent in the haloalkyl groups among the catalyst; of our invention. Preferably the halogen should be in the 1 position in the side chain.

As explained above, we may also employ such compounds having additional alkyl, alkoxy, bymxy, halogen or haioalkyl substituted in the The following examples, given as illustrative and not as limitations of our invention, illustrate the activity of the group of photochemical catalysts generically defined above:

l'zample 1 A one per cent solution of alpha-'chlormethyl naphthalene was made in methyl methacrylate monomer and exposed to direct sunlight in a glassvial. Alikeglassvialcontainingmethyl mcthacrylate monomer and no catalyst was also exposedtodirectsunlightforthesametimeasa control blank. The catalysed monomer set to a. hard gel in one-half hour while the uncatalyzed monomer did not undergo any apparent polymerisation.

trample 2 In a like experiment a 1% solution of the alpha-hromoethyl naphthalene caused the formation of a hard gel oi the methyl methacrylate monomer in one hour when exposed according to the procedure of Example 1 under somewhat difl'erent sunlight conditions. In like manner a 1% solution of the beta-bromoethyl naphthalene sene rings either not further substituted by other (a in methyl methacrylate caused the formation of a hard gel under the same conditions in about one hour.. The uncatalyzed monomer was apparently unpolymerized in all of the above cases.

Example 3 Example 4 A 1 solution of-beta-chlormethyl naphthalene was made in methyl methacrylate monomer and treated in the manner described for Example 3. It gelled in five hours and set solid and hard (containing about 60% polymer) in seven hours, while the uncatalyzed monomer blank was substantially' unpolymerized and showed substantially no change in viscosity.

Example 5 2% solution of 1,5 dichlormethyl naphthalene was subjected to the procedure of Example 3 and cured hard in One hour and thirty minutes. In the same experiment a 2% solution of alphachlormethyl naphthalene in methyl methacrylate monomer cured hard in two hours, while the blank of the uncatalyzed methyl methacrylate was substantially unpolymerized.

Example 6 1% solution of beta methoxy-alpha chlormethyl naphthalene was exposed according to Example 3 and gelled hard in three hours while the blank was unailected.

Example 7 A ring chlorinated chlormethyl naphthalene was obtained by chlorination of a mixture of alpha and beta methyl naphthalene under conditions such that chlorine went into the ring as well as the side chains. The mixture of alpha and beta methyl naphthalene was distilled and the vapor passed through a Pyrex tube into which chlorine was introduced at a rate to establish a mixture in the tube of about 0.75 molof 012 to 1 mol of the methyl naphthalene. The tube was illuminated by a quartz mercury vapor lamp. The vapor and gases passing from the tube were condensed and the condensate refractionated by distillation at 17 m. m. absolute pressure. The fraction boiling between 172-l79 contained mixed alpha and beta-chlormethylnaphthyl chloride. The fraction boiling between 176 and 187 contained chlormethylnaphthyl chloride of higher degrees of ring chlorine substitutions. A 1% solution of each of the fractions was made in methyl methacrylate and exposed to sunlight according to the procedure. of Example 1 and others to the ultra-violet light according to the procedure of Example 3 with the following results:

Uncatalyzed blanks of the methyl methacrylate monomer showed substantially no change when exposed under the conditions and for the times given in the above table.

Example 8 Alpha-chlormethyl beta naphthol was formed by mixing equimolar quantities of beta naphthol and formaldehyde (40% solution) and adding slowly with vigorous stirring an equimolar amount of hydrochloric acid at room temperature. Water was added with vigorous stirring as soon as the reaction product formed a homogeneous syrup. The water solution was neutralized with sodium carbonate. The oily layer was separated and may be used as a photo-. polymerization compound or the alpha-chlormethyl beta naphthol may be purified by dissolving in ether and shaking with sodium carbonate or other suitable drying agent. The ether may be evaporated to give a viscous material which if allowed to stand will harden into a high molecular weight polymer.

The reaction product, particularly in its unpolymerized state or partially polymerized state, is an active photopolymerization polymer and is as active as alpha-chlormethyl naphthalene.

This when used in place of alpha-chlormethyl naphthalene in the procedures of Examples 1 or 3 is as active and perhaps more active than alphachlormethyl naphthalene. When similarly irradiated the uncatalyzed resinophor showed substantially no change.

Example 9 1% solution of gamma-chlormethyl phenanthrene in methyl methacrylate was treated according to procedure of Example 3 and resulted in polymerization to high viscosity while the blank with no catalyst added showed no change in this exposure.

The rate of polymerization and/or its induction period was affected by the per cent of catalyst employed but the effect was apparently exponential in character.

Example 10 This example illustrates the eifect of the concentration of the photopolymerization catalyst on the rate of polymerization of methyl methacrylate in bulk at 30 C. A series of methyl methacrylate samples containing .003, .03, .3, and 3.0% of alphachlormethyl naphthalene was prepared and placed in glass vessels. The samples were then irradiated with light from a 250 watt mercury vapor lamp, operating at a distance of 3 inches from the specimens. The specimens were allowed to polymerize to a solid (about polymer). The time required for this degree of polymerization is given in the second column.

Per cent alpha-chlormethyl naphthalene Time in hours 33 5t. oIoiIIIIIIII 11." 0.003 25. None (control) Still ,fluid after hours exposure.

7| catalyst employed will depend, therefore, on the desired rate of polymerization and also on the specific activity of the particular catalyst under consideration as well as on the intensity of the illumination by the polymerizing light. It will also be found that an excessive concentration of catalyst may interfere with the polymerization and be detrimental. Thus the rate of acid may increase with increase of concentration of catalyst as described above, and if the catalyst concentration is made excessive it may again decrease. that is, there is an optimum concentration for each catalyst monomer and photopolymerisation condition.

With these considerations in mind it will be found that from about .00l% to about of catalyst will be, in most cases, a useful concentration to employ.

The photochemical polymerization of the resins apparently is greatest by light of wave length lem than about 3500 Angstrcms. Usual photochemical sources of actinically active light such as mercury or carbon are light or direct sunlight or incandescent filament lamps are thus eiiective.

The relative eflectiveness of various wave lengths and the photochemical nature of the process is illustrated by the following experiment.

Example 11 u on wave lengtlu below Angstroms Cured. Do. Do.

. Very, very slightly viscous. Did not cure.

Did not cure.

Do. Do. Dm

The relative effectiveness of the various wave lengths ofllght will in part depend upon the nature of the catalyst and its concentration as well as on the nature of the resinophor or resulting polymer, as well as the intensities of illumination, and the above table is not intended to indicate that wavelengths longer than 3450 are ineflective other than under conditions specified in the example. Since usual light sources, such as the ultra-violet light sources. as. for example. mercury or carbon are light or visible light sources. such as incandescent lamps or sunlight, contain suitable actinically active wave lengths they form suitable sources of illumination for the purpose of our invention.

Examples of the activity of the class oi catalysts for various types of polymers'are illustrated by the following:

Example 12 A 3% solution of alpha-chlormethyl naphthalene was dissolved in the following monomers and subjected to irradiation according to the 8 proeedured escribedinnamplesferthetimes indieatedineolmnns2,3,and4:

sme ma- Momma Employed 42 Hrs.

Styrene and dlethyl Bubbcy.

maleats mixed in equi hlanks of each 8! the above monomers (no eatalyst) showed substantially no change after the above exposures.

trample 18 1% alpha-chlormethyl naphthalene was dissolved in equimolar mixtures of the following monomers and subjected to illumination by sunlight according to the procedure of Example 1 with the following results:

Time of iilumination State oi Monomers Product Hours Vinyl acetate and methyl mcthacrylate. 3 Methyl methacrylate and methyl- 4) acrylate.

Hard. Do.

Blanks of each of the above uncatalyaed monomers when subjected to irradiation for the times indicated above showed substantially no change.

Example 14 A liquid mixture of triethylene maleate and styrene with a substantially equal ratio of styrene to maleate groups and containing 1% of alpha-chlormethyl naphthalene was irradiated according to the procedure of Example 3 for the times indicated in the table with the following results:

Time of Irradiation Ststeol' Proda 4 Hours Gelled hard. 10 Hours Cured hard.

The blanks (no catalyst) showed substantially no change after similar exposure for 19 hours.

Example 15 The copolymer of the previous Example 14 was mixed with 1% of beta methoxy-alpha-chlormethyl naphthalene and exposed to direct sunlight according to the procedure of Example 1. It gelled in one hour and was hard in three hours.

The blank containing no catalyst showed substantially no change after the three-hour exture control to prevent excessive generation of heat during polymerization is desirable. The illumination may be by a light source positioned above the exposed surface of the container or where the container is light-transmitting, as when it is of glass, it may be made from a light source through the glass vessel. There are now available ultra-violet light sources which may be suspended inside the reaction vessel and these may be conveniently used.

The vessel may be of the desired shape to form a mold to give a molded casting of desired shape. Photochemical laminations may also be made as when the sheets being laminated are lighttransmitting as, for example, if they be made of fibre glass, glass sheets, or plastic mesh or plastic sheets. In such case the laminate, especially when the resin employed is of the contact type, may be formed into the desired laminate of the desired shape and set by photochemical means, as by exposing the laminate to sunlight or to a special source of illumination as indicated above.

The casting or the laminate may be further baked if further hardening of polymerization oi the photopolymerized product is desired.

The photopolymerization process may be carried out at low or at elevated temperatures but as the temperatures become high, bubbles and striations may be formed in the castings. Since the catalyzed photopolymerization permits of rapid polymerization at low temperatures to produce bubble free castings, it is usually preferable to cause the reaction to occur at ordinary atmospheric temperatures and, if desired, even at low temperatures, 1. e., at temperatures ranging from to 50 C. These temperature limits are not critical and merely indicate that heat is not necessary to cause the reaction to proceed.

However, since thermal polymerization is not inhibited by these catalysts and may also be carried out simultaneously, elevated temperatures are not a hindrance so long as they are not so high as to cause bubbles or other defects, as will be recognized by those skilled in the art.

Photopolymerization employing our catalyst may also be carried out in a solution of the monomer or partial polymer in a volatile solvent. Thus, the monomer or partial polymer containing the catalyst is dissolved in a solvent and introduced into a vessel and illuminated. Usual precautions against the loss of solvent and cooling, where necessary to avoid overheating, may be employed. The solution is illuminated in a manner similar to that described above for bulk polymerization. Instead of polymerizing a bulk quantity solution in a vessel, we may saturate a sheet or a plurality of sheets arranged in laminated form with such solution and photopolymerize in a manner similar to that described above. The solvent may be evaporated either during, prior to, or subsequent to the photopolymerization.

The following example illustrates the effect of our catalyst in photopolymerization of a solution of a monomer in a solvent:

Example 16 alpha-chlormethyl naphthalene. The two s0lu-' tions were exposed simultaneously in glass containers to the light of a 200 watt mercury vapor quartz lamp at a distance of six inches from the lamp. The yield of polymer precipitated from solution was as follows:

Per cent For catalyzed monomer 30.5 For uncatalyzed monomer parts of methyl methac'rylate containing 1.5 parts of alpha-chlormethyl naphthalene were mixed with 200 parts of water containing 1 part of methyl starch in a glass vessel provided with a suitable reflux condenser. The source of light was a 250 watt quartz mercury lamp at a distance of three inches from the vessel. The time of exposure was seven hours. The temperature of the vessel was maintained sufiiciently elevated to cause a refluxing of the vaporized water. Constant stirring was maintained during the period of illumination. After seven hours, the granular product was separated, washed, and dried. A quantitative yield of polymer was produced.

When a similar dispersion of the monomer, but not containing the catalyst, was treated in the above manner no polymer was formed.

We may, if desired, add conventional thermal polymerization catalysts, such as the peroxide catalysts like benzoyl, lauroyl, tertiary butyl hydrogen peroxide in addition to the photopolymerization catalyst. Thus, photopolymerization may be carried on either at low or at elevated temperatures and the photopolymerized gel may be hardened further by heating the photochemically gelled product. This permits of a relatively low temperature setting of the resin to pro-bodied form or to a relatively hard casting which may then be baked at an elevated temperature.

This is equally true when laminating. Thus, the laminate may be set at relatively low temperature by photopolymerization and the laminating bond hardened by baking.

By this process not only is the clearness and the integrity of the hardened gel increased, but the photopolymerization step accelerates the total time of cure.

The rate of photopolymerization may also be increased by suitable concentrations of the catalyst as indicated above.

When oxygen is found to deleteriously affect the rate of polymerization, vessels containing the material undergoing photopolymerization may be evacuated or an inert gaseous atmosphere, as, for instance, a nitrogen atmosphere, may be employed.

The above description and examples are intended to be illustrative only. Any modification of and variation therefrom which conforms to the spirit of the invention is intended to be included within the scope of the claims. Matter not claimed herein is claimed in our co-pending application, Serial No. 776,872, filed on September 29, 1947.

We claim:

1. As a new composition of matter a catalyst photopolymerizable resinophoric compound consis ing essentially of an ethylenically unsaturated photooolymerizable resinophor containing dispersed therein a minor proportion oi'a photopolymerization catabst consisting essentially oi a haloalkyl substituted poiynuclear aromatic compound containing condemed bensene ring in which the halogen is in the 1 position in the alkyl substituent.

2.Asanewcompositionoimatteracatalyst photopolymerizable resincphorlo c'ompoumd consisting essentially of an ethylenicalb unsaturated photopolymerizable containing dispersedtherelnamlnorproportionoiaphotopolymerization catalyst essentially oi a haloalkyl substituted polynueiear aromatic compound in which the halogen is in the 1 position in the alkyl substituent and is chosen from the group consisting of chlorine, bromine, and iodine.

3. In the composition of claim 2, said polynuclear aromatic compound containing in addition to the haloalkyl ring substituent a substituent chosen from the group consisting of the alkyl, alkoxy. hydron. halogen, and haloalkyl ring substituents.

4. In the composition oi claim 2 said haloalkyl having an alkyl chain length oi. more than one carbon atom.

5. In the composition oi claim 4, said polynuclear aromatic compound containing in addition to the haloallryl ring substituent a substituent chosen from the group consisting oi the alkyl, allroxy, hydroxy, halogen, and haloalkyl ring substituents. I

6. In the composition of claim 1, said polynuclear aromatic compound containing in addition to the haloalkyl ring substituent a substituent chosen from the group of the alkyl, alkoxy. hydro. halogen and haloaikyl ring substituents.

"I. As a new composition oi matter, a catalysed photopolymerizable resinophoric compound comprising an ethylenically umaturated photopolymerizable resinophoric compound and a minor proportion oi 1,5 dichloro-methyl naphthalene.

8. As a new composition of matter, a catalned pho opolymeriaahle resinophoric compound comprising an ethylenically unsaturated photopolymerizable resinophoric compound and a minor proportion of chlormethylnaphthyl chloride.

9. As a new composition of matter, a catalysed photopolymerizable resinophorlc compound comprising an ethylenically unsaturated photopolymerizable resinophoric compound and a minor proportion oi beta-methoxy-alpha-chiormethyl naphthalene.

10. A process oi photopolymerization comprising the steps of adding to an ethylenically unsaturated photopolymerizable resinophor from about .00l% to about 6% of a photopolymerization catalyst consisting essentially of a haloalkyl substituted polynuclear aromatic compoimd. in

which the halogen is in the 1 position in the alkyl substituent. and exposing the same to irradiation by actinically active light to polymerize the resinophor.

ILTheprocessseti'orthinclaimlOinwhich the halogen is chosen from the group consisting of chlorine. bromine, and iodine.

12. The process set forth in claim 10 in which the catalyst contains a second substituent chosen from the group consisting of the alkyl, alkony,

13. The process set forth in claim 10 in which the haloalkyi has an alkyl chain oi. more than one carbon atom and the halogen is chosen iron the group consisting oi chlorine, bromine. and iodine 14. The process of photopolymerization comprising the steps oi adding to an ethylenically imsaturated photopolymerizable resinophor from about 901% to about 6% of a photopolyme'risation catalyst consisting essentially oi a haloalkyl substituted polynuclear aromatic compound, in which the halogen is in the 1 position in the alkyl substituent, said haloalkyl having an alkyl chain of more than one carbon atom, and exposing the same to irradiation by actinically active light to polymerize the resinophor.

15. A process of photopolymerization which comprises adding to an ethyienically unsaturated photopolymerizable resinophor a minor proportion of 1,5-dichlormethyl naphthalene in the proportion of from about .001% to about 5% of the naphthalene compound, and subjecting the same to irradiation by actinic light to polymerize the resinophor.

16. The process of photopolyrnerization comprising the steps of adding to an ethylenically unsaturated photopolymerizable resinophor chlormethylnaphthyl chloride in the proportions of from about .001% to about 5%, and subjecting the mixture to irradiation by actinic light to polymerize the resinophor.

17. A process of photopolymerization comprising adding to an ethylenically unsaturated photopolymerizable resinophor from about .00l% to about 5% of beta-methoxy-alpha-chlormethylnaphthalene, and subjecting the mixture to irradiation by actinic light to polymerize the resinophor.

18. The process set forth in claim 10 in which the alkyl group is composed of more thanone carbon atom, said halogen being chosen from the group consisting oi chlorine, bromine, and iodine.

19. A process according to claim 10 in which the alkyl group is composed of more than one carbon atom and in which the halogen is chosen from the group consisting of chlorine, bromine, and iodine. and the compound contains a second substituent chosen from the group consisting oi the alkyl. alkoxy. hydroxy. halogen, and haloalkyl ring substituents.

20. As a new composition of matter a catalyst photopolymerizable resinophoric compound consisting essentially 01' an ethylenically unsaturated photopolymerizable resinophor containing dispersed therein from about .00196 to about 6% oi a photopolymerization cataLvst consisting essen- REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 1.891 203 Ambros et al. Dec. 13, 1932 2,207,686 Schwarcman July 9, 1940 2,326,736 Adelson et a1 Aug. 17, 1943 

1. AS A NEW COMPOSITION OF MATTER A CATALYST PHOTOPOLYMERIZABLE RESINOPHORIC COMPOUND CONSISTING ESSENTIALLY OF AN ETHYLENICALLY UNSATURATED PHOTOPOLYMERIZABLE RESINOPHOR CONTAINING DISPERSED THEREIN A MINOR PROPORTION OF A PHOTOPOLYMERIZATION CATALYST CONSISTING ESSENTIALLY OF A HALOALKYL SUBSTITUTED POLYNUCLEAR AROMATIC COMPOUND CONTAINING CONDENSED BENZENE RING IN WHICH THE HALOGEN IS IN THE 1 POSITION IN THE ALKYL SUBSTITUENT.
 10. A PROCESS OF PHOTOPOLYMERIZATION COMPRISING THE STEPS OF ADDING TO AN ETHYLENICALLY UNSATURATED PHOTOPOLYMERIZABLE RESINOPHOR FROM ABOUT .001% TO ABOUT 5% OF A PHOTOPOLYMERIZATION CATALYST CONSISTING ESSENTIALLY OF A HALOALKYL SUBSTITUTED POLYNUCLEAR AROMATIC COMPOUND, IN WHICH THE HALOGEN IS IN THE 1 POSITION IN THE ALKYL SUBSTITUENT, AND EXPOSING THE SAME TO IRRADITION BY ACTINICALLY ACTIVE LIGHT TO POLYMERIZE THE RESINOPHOR. 